Heaven and Hell are described in the Bible and the Koran as places commensurate with the rewards deserved by those who have functioned in the Service-to-Others or Service-to-Self orientation - in the minds of the authors of these books, who in the main were in the Service-to-Others when they authored the books. For primitive peoples, who relied upon fire for cooking and warmth, catching on fire was a known dilemma, and the pain from such an accident not unknown. Thus, as one of the most excruciating pains, and one slow to heal and suffering the injured much pain during the healing process, eternal fire was the worst of the worst.
Similarly, the higher one went, physically speaking, the better life got. Specifically we are describing living on hill tops versus valleys, and having the higher campground versus one downhill. As the saying goes, shit flows downhill. Valleys have dampness and humidity, lizards and snakes and insects galore. Hilltops have breezes and vistas. Better yet is what the birds enjoy, high in the skies. Nothing can touch them, and as good as the hilltops are, the skies must be better! Thus, heaven is viewed as up in the skies, and the higher the better.
In fact, the just deserts of the Service-to-Others and Service-to-Self are not Heaven and Hell, but to live with their own kind, which is in a manner of speaking, to our way of thinking in any case, a type of Heaven and Hell.